1. Field of the Invention
The present invention relates to an assembly for use in a crankcase ventilation system of an internal combustion engine with at least one cylinder having a piston and a combustion chamber. The present invention also relates to a crankcase ventilation system for use in an internal combustion engine, wherein the crankcase ventilation system comprises such an assembly. The present invention further relates to an internal combustion engine comprising a crankcase ventilation system as mentioned above. The present invention also relates to a vehicle comprising an internal combustion engine as mentioned above. The present invention further relates to a method for providing an assembly according to the present invention in a crankcase ventilation system of an internal combustion engine.
2. Description of the Related Art
Crankcase ventilation systems are commonly known and are used in internal combustion engines, such as diesel, gasoline and liquefied gas powered direct injection engines, for removing blow-by gases, i.e. gases that leak past piston rings, and other vapors from the engine's crankcase. To accomplish this, a crankcase ventilation system is constructed and arranged for allowing fresh air that is drawn from an air cleaner unit of an air intake system to enter the engine's crankcase via a first duct, which is generally indicated as breather duct. Furthermore, the crankcase ventilation system comprises elements constructed and arranged for purging unwanted gases and/or vapors from the crankcase. This is usually accomplished by providing a second duct, which is generally indicated as purge duct. The purge duct is arranged between a valve cover and an air intake duct. The purge duct comprises a control valve that is constructed and arranged for controlling the amount of gases and/or vapors out of a crankcase that enter the air intake duct as a function of engine load and/or throttle valve opening. The purge duct is usually connected to the air intake duct at a position where air pressure in the air intake duct is lower than the pressure in the crankcase when the engine is running. This location is usually in the vicinity of the throttle valve. Instead of venting the gases and/or vapors to the outside environment they are fed back into the air intake duct and re-enter a combustion chamber as part of a fresh charge of air and/or fuel.
An amount of air from the air cleaner unit is fed into the engine's crankcase via the breather duct. Once inside the crankcase, the air circulates around its interior thereby picking up and removing among others gases and byproducts of the combustion process and vapors, e.g. water vapor, which might include dissolved chemical combustion products and/or byproducts. These gases and/or vapors pass an oil separator element, e.g. a baffle or a mesh, in order to trap oil droplets before being drawn out of the valve cover through the control valve of the crankcase ventilation system, into the air intake duct.
As mentioned above, the crankcase ventilation system relies on the fact that, while the engine is running under light load and moderate throttle opening, the pressure in the air intake duct is lower than the air pressure in the crankcase. As a result of this lower pressure, air is drawn into the air intake duct, thereby pulling air consecutively from the breather duct through the crankcase, where it dilutes and mixes with the abovementioned gases and/or vapors, through the control valve of the crankcase ventilation system, and into the air intake duct. If the air pressure in the air intake duct is higher than that in the crankcase, the abovementioned control valve reduces its flow opening to at least strongly reduce reversal of the exhausted air back into the crankcase.
A drawback of conventional crankcase ventilation systems is that after the engine has been shut down residual gases and/or vapors out of the crankcase can accumulate in the air intake system as the control valve of the crankcase ventilation system is constructed and arranged such that it never completely closes the purge duct. As a result, the residual gases and/or vapors out of the crankcase at least partly replace the air present in the air intake duct of the air intake system. When the engine has been shut down for a long period of time, typically 12 hours or more, the engine frequently fails to start at a first attempt. This is caused by an over-rich mixture comprising air, residual gases and/or vapors out of the crankcase and/or fuel, which is drawn into the combustion chambers during cranking.